1. Field of the Invention
The present invention relates to a horn switch mechanism mounted on a steering wheel of an automobile.
2. Description of the Prior Art
A conventional horn switch mechanism for a steering wheel is shown in FIGS. 1 and 2 (refer to U.S. Pat. No. 4,594,486).
This conventional horn switch mechanism HO is composed of a stationary contact plate 2 made of sheet metal and a movable contact plate 3 made of a metal plate spring.
The movable contact plate 3 is of turned H shaped (turned by 1/4 revolution) viewing from the upper side. The longitudinal bar portion of the turned H shape defines a base portion 3a disposed to the side of the stationary contact plate 2 and lateral bar portions of the turned H shape define contact portions 3b extending upwardly from the base portion 3a.
Depressing plate 4 is provided on the upper surface of the contact portions 3b of the movable contact plate 3. The depressing plate 4 is restricted at the separation distance from the stationary contact plate 2 by a restricting means (not shown) and electrically insulated from the stationary contact plate 2. A horn pad 1 is disposed above the depressing plate 4.
The base portion 3a of the movable contact plate 3 is fixed to the stationary contact plate 2 through an electrical insulation plate 5 made of plate-shaped synthetic resin having an external configuration similar to that of the base portion 3aan electrical insulation ring 6 made of circular ring shaped synthetic resin and a terminal 9 with L-like cross-section by a rivet 7 which is conductive.
The stationary contact plate 2 is secured to an energy absorber 10 made of sheet metal fixed to the steering wheel body, such as a boss (not shown) of the steering wheel, and the stationary contact plate 2 is electrically connected to the negative terminal of a horn control circuit through the energy absorber 10.
On the other hand, the movable contact plate 3 is electrically connected to side of a positive terminal of the horn control circuit through a lead wire 8 connected to the terminal 9.
In the horn switch mechanism HO, the horn pad 1 is depressed whereby the contact portions 3b of the movable contact plate 3 are depressed through the depressing plate 4 and contacts 3c of the contact portions 3b are brought into contact with contacts 2a of the stationary contact plate 2 and the horn is operated.
In the conventional horn switch mechanism HO, however, the movable contact plate 3 is locked by the rivet 7 to the stationary contact plate 2 through the electrical insulation plate 5, the electrical insulation ring 6 and the terminal 9 and therefore the number of the parts to be assembled is great.
Also at the locking by the rivet 7, since the four parts, i.e., the movable contact plate 3, the electrical insulation plate 5, the electrical insulation ring 6 and the terminal 9, must be arranged to the stationary contact plate 2, care must be taken so that various parts are not shifted and therefore the assembling work becomes troublesome.